The National Emissions Standards for Hazardous Air Pollutants ("NESHAP"), Part 61, Subpart L promulgated in 1989 (Federal Register, V. 54, No. 177, p. 38073 et seq., Sep. 14, 1989), decree that all coal tar tanks must be sealed and gas-blanketed because of emissions of benzene which otherwise occur. Exemptions from gas-blanketing may be obtained if alternative methods are demonstrated to reduce benzene emissions from the tanks by 98%. Emissions should not in any event exceed 500 ppm by volume.
The gas-blanketing of tar tanks is expensive both initially and as an on-going enterprise. Regardless of the particular governmental standards, it is recognized that benzene emissions from storage tanks and during transport present a problem which should be addressed. We have therefore invented a practical alternative.
Processing of coal tar of various types is a common practice in the coke making industry. However, the removal of benzene as we perform it is not known to us, and the treatment of coal tar in two stages to make both a low-benzene tar and a low-benzene sludge fuel has not been done to our knowledge.